Can I travel by flight using my passport to another state within without any problem?

As long as your passport is valid, you will be fine.

About OPT and status

Duplicate question. You are paying a fee for your school's international service. Consult with them.

Regarding MotionFiling and f1-visa

More likely you need a new F1 visa. You international office can help you better.

Since we got married without a big ceremony, will the Immigration interviewer see that as a red flag?

Having a big wedding ceremony is not one of the most important factors. The more important is document such as joint ownership. Congrats and good...

Can I work reduced hours on H1B ?

In your case, an amended H-1B petition is needed. Company's attorney can help you.

Selected as the best answer

How could I work on OPT in IT field being from mechanical background? Also would there any problems for H1 b in future.

Generally your OPT must be related to the field of your study. Contact your international office and they should be able to help you.

What forms Does my employer have to fill for me to change my status to work visa ? Form I- 129 and form I-539 or what form ??

Company's immigration attorney can help you with this matter.

H1b transfer approved but want to continue to work for current employer.

This matter should be discussed with the company's immigration attorney.

How can I spend maximum time out side USA and still come here once a year? Will I be ban to enter US with different visa?

In order to be eligible for immigration benefit, you have to maintain residency in the United States.

You have to discuss these issues with your school (as I see you have marked F1).