Question about sales tax (Texas)

I had a question I was hoping someone could help me with if they’re sure of the answer. This is regarding a sale in Texas.

If I do a lease buyout on Vehicle A that does not include sales tax, but I trade in that vehicle towards Vehicle B, how does sales tax work on that? I guess my question is multipart.

1. How long do I have before I have to pay the sales tax on Vehicle A? I believe it is 30 days...extended to 90 because of COVID but not 100% sure.

2. When does the count of days start from question 1? The day the Bill of Sale is signed? The day the title transfer application is submitted? The day the actual title is transferred? Etc.

3. If I trade in Vehicle A before the timeframe for paying taxes expires, I don’t have to pay taxes on Vehicle A, correct?

4. To continue with question 3, if I trade in Vehicle A, do I get the sales tax credit towards Vehicle B? I know I technically didn’t pay the taxes on Vehicle A, but figured I would ask to help with the next question.

5. If a dealership does give me the sale tax credit (knowing or unknowing that I didn’t pay taxes on Vehicle A), but I didn’t actually pay the taxes on Vehicle A, what happens? Do they bill me for it? Will anyone even notice?

Any useful information would be greatly appreciated!

I’m not trying to be shady, or “pull a fast one”. I’m in the process of buying out my lease and am potentially in the market to trade it in towards one with more bells and whistles. If I can save a few thousand on sales tax by doing that now, it will help me decide whether I want to do it now or wait until later down the road.