'Accuse of doing'/'Open on Sundays'

1) "Someone accuses someone OF doING something" is the formula.
The person accused is the object of the verb "accuse". The act that person may have done is introduced by "of" and is expressed with a gerund (ING form).

David accused Matt of stealing.
Jenny accused her sister of cheating at cards.

Someone - Monika
now
accuses - accuses
someone - those who backed her
OF - of
doING - kidnappING (her)
and
(OF)
doING - forcING her to tell lies.

2) In the case of expecting someone to behave a certain way, which I believe you are aiming at, it is "expect of". "He was very rude - something I never would have expected of him."
However, you use "expect from" in other situations if an exchange is involved: "I wasn't expecting a letter from her." "A letter was not expected from her at this time."

3) Three correct possibilities (all simple sentences) are:
Is it open on Sunday(s)?
Does it remain open on Sunday(s)?
Is it going to remain open on Sunday(s)?

"Is it remain open on Sunday(s)?" is not at all correct!

It is the question form of the statement "It remains open on Sundays".

Any statement with the verb in the "s" form (remains) is transformed into a question by putting "does" at the beginning (never "is") and removing the "s".

It remains open on Sundays. Does it remain open on Sundays?

This car goes very fast. Does this car go very fast?

Your brother likes to water ski. Does your brother like to water ski?

The sign says "Stop". Does the sign say "Stop"?

Any of these is wrong if you replace "Does" with "Is"!

These are all wrong: Is it remain open on Sundays? Is this car go very fast? Is your brother like to water ski? Is the sign say "Stop"?

Don't confuse the examples above with sentences which have the verb "to be". Such sentences don't use "does" at the beginning of the question form.

It is open. Is it open?

Hope that helps.