I don't think I created any of these - just edited them to indicate that cycling is prohibited.

They are entirely within a 20 mph zone, and only accessible from streets with 20 mph signage. There is no contradictory signage at the entrance, so that is the speed limit that applies.

The same is true at every other example where a dual carriageway ends and becomes a single carriageway. Each carriageway of the dual carriageway is represented as a line following the centre line of that carriageway - the single carriageway is represented as a line following the centre line of that. This necessarily involves bending the ends of each of the duel carriageways to meet the end of the single carriageway. This is just an example of exactly that.

Also, odd definitions are also used in the UK. OSM uses "Trunk" for primary roads and "Primary" for bog standard A roads. In the official road hierarchy "Trunk" is applied to the the strategic highway network managed nationally - and does mot include this road.

On the editor the default is shown as "bicycle=Not Specified" for trunk roads (exactly the same as for pavements). Primary roads are OK,

I would not tag it at all - there is simply one continuous paved surface with no kerbs or lane markings. It looks as if it has been widened at some point and the edging stones of the original road and pavement have been left in place.

It is not a driveway because (as you observed) it serves more than one property, whereas in OSM a driveway is defined as minor service road leading to a specific property. For the same reason it access cannot be private – since access is needed to reach destinations further down the road.

It is common for early 21st century culs-de-sacs to be designed in this way, with the last few houses on each twig of the tree being constructed to a lower standard, with shared surfaces and no turning circle at the end. These public highways on which the normal rules of the road (including speed limits) apply.

These stretches tend not to be adopted by the local highway authority, but that is just a matter of who is responsible for the maintenance – not an access limitation. Hence, you cannot deduce access restrictions based on land registry plots. Defining access as private would mean that the first plot of land that any unadopted cul-de-sac crossed would be a ransom strip.

Have you discussed this with the landowner (National Trust)? They have been systematically tagging access for paths on their land. See note on previous edit:

Paths data. All edits have been made as part of an organised editing activity agreed with OSM board members, and in consultation with National Trust rangers. For more info please see: Organised Editing/Activities/National Trust Paths - OpenStreetMap Wiki

This does seem to be rather an obsession on your part.
In this case the private parts of the drives have been separated from the the parts within the highway boundary.

If it is not a crossing then it was the original tagging it as a crossing was incorrect.

These are simply junctions.

Cycling on pavements is illegal unless signed otherwise - so it is the absence of any signs allowing cycling that is the key.

So the point at which the pavement heading out from Lascaster ceases to be shared use is actually at the junction before the dismount sign. You can see shared use signs and give way markings on the pavement heading west, but not east. And you can see cycleway markings in each direction at all the junctions it crosses till it reaches the other end at Lansil Way.

I guess the Dismount Sign in this case is just a reminder to those who inadvertently continue to ride illegally on the pavement. It has no legal meaning and are used (some would say abused) for a wide range of different purposes.

Those traffic signals have nothing to do with the crossings - just traffic flows from other arms of the junction. ie the junction is signal controlled but the crossings are not.

You suggest that "Pedestrians cross when the lights are red", but there is no such time. If they are red for traffic approaching from one arm then they will be green for traffic approaching from a different direction. There is no time allocated for pedestrians at all.

The issue of buttons is entirely irrelevant - the issue is the absence of any signal control of the crossing. There is nothing that a button could request.

It is the case that some of the crossings only cross a single lane approaching from one direction so there are times when that is held at red. But this still does not constitute a signal controlled crossing. At a signal controlled crossing when the pedestrian signal turns red then the carriageway signal must remain on red long enough for pedestrians to cross - and on puffin crossings this is detected. At these crossings the traffic may be stopped, but could start at any instant.

It is a zebra (ie pedestrian only) crossing.
Highway Code rule 81:
"Do not ride across a pelican, puffin or zebra crossing."

You need signage to indicate that a formal crossing may be used by cyclists or horses - by default they are for exclusive pedestrian use (same as for pavements). In the case of a zebra crossing this would be indicated by a parallel crossing edged by large white square dots. This zebra crossing has no such markings, therefore it is not a cycle crossing.

So presumably when you visited a year ago you will have noticed the sign prohibiting cycling, which begs the question - why did you ask if it was recent?

It is not and has never been a cycle route despite Sustains misleading mapping. If folk want there to be a cycle route they need to lobby the council to create one - not put misleading tags on OSM.

Unfortunately the default tagging for pavements is "Not Specified" - exactly the same as for trunk roads. This confuses cycle routing applications into recommending illegal routes.

The ways represent ways of finite width as linear features, The line represents the whole width of the way - not a zero width line.. Similarly, road junctions are mapped as a point even though they occupy a finite area.

So, at a junction between a residential road and a A road you meet at a point in the centre of the A road - you don't map a tiny stub of A road from the centre to the give way line.

No, the NO CYCLING sign is longstanding. It was there over 15 years ago:
https://maps.app.goo.gl/aYbpnChBXXLf8kyQ8

I suspect the other mapper had not visited the site and was trying to mislead cycle routing tools to follow Sustrans mapping, which often fails to correspond to legal or practical routes.

The map needs to reflect the world as it is - not the wishful thinking of Sustrans.

Unfortunately the default tagging for trunk roads is "Not Specified".

Pavement cycling is ILLEGAL in the UK.
cycling = no is therefore the correct designation. Please stop deleting my edits.

That would make no sense.

Tactile paving is only ever used at the ends of a crossing to indicate to visually impaired people that they are about to step onto the carriageway. See:
tactile_paving=yes
Sometimes crossings are not provided with this and sometimes the are - hence the tag. But tactile paving is never applied all the way across.