Partner has difficulty with stairs and walking more than 2-3 blocks at a time. Suggestions?
When looking for hotels, there should be info about the presence/absence of elevators.
As for tours, you need to look at their itinerary , or inquire, just how much walking is involved.
Your question is so broad, it is difficult to offer specific suggestions
I found a few hotels that stated no elevator, can you assume the others do have an elevator?
Make no assumptions. Ask specific questions about elevators and access to a hotel from street level.
Make no assumptions.
Cannot overemphasize this point
All of hotels( new ones) they have elevator.
Since you posted in the Turkey section of the Forum, I don't know if you're asking about Istanbul or somewhere else.
However, in general, it is very important not only to make no assumptions, but to find out particulars of each room you are looking to book (not just the hotel in general). For instance, I've had hotels where you have to climb a flight of stairs to get to the elevator, and other hotels where the elevator does not go to all the floors. Furthermore, remember that in Europe, what we in the US call the "first floor" is actually called the "ground floor"; their "first floor" is ALWAYS up a level from the ground. So, if you want to avoid stairs or elevators, you need a ground floor room.
It's also common for restaurants to be on the ground floor, but for the bathroom to be up or down a flight of stairs - often steep with no elevator.
Rick used to have a book called Easy Access Europe. It's out of print and outdated, but he has it here on the website for free. It doesn't have specific information on Turkey, but does have lots of tips to get you started, as well as resources to contact for further and more up to date information. https://www.ricksteves.com/watch-read-listen/read/easy-access-europe
It's worth being aware that "handicapped" is seen as a slightly offensive term by some in Europe. Searching for "disabled" might get you some more/different results.