hi greetings from the philippines !!!

I need your help on the following. I don't think my English is all that bad, but I frequently get confused when trying to use the following verbs. A detailed description with examples is as follows:

She has to go. (Present)
She had to go. (Past)

May I come in?
Might I come in?

On the table
In the table
At the table

That is mine- present tense?
That was mine - pastense?

both are correct right????

But then again, the kind of "inflection" we're concerned about in this discussion is temporal in nature, and not morphological in form. That is, if it's not called "inflection", then what is it called? Is there a difference between run/ran and has to/had to, and if not, is has to/had to not a true modal? Moreover, why is it that in order to get "could" to bend time, we have to negate it?

She has to go. (Present)-- right
She had to go. (Past) -- right

May I come in? -- polite
Might I come in? -- a little bit more polite

On the table -- yes, on the top
In the table -- only as a shortened form of in a/the drawer of the table
At the table -- possibly, if the thing is big and the table is 'way over there.

That is mine- present tense? -- yes
That was mine - past tense? -- yes

Bon voyage!

thank you so much Mister Micawber!!!! you are of great help!!!