Employer Changing Notice Period Terms and Withholding Salary

I'm a MERN stack developer at a small company (~10 employees). This is my first job, and I've been working here for 9 months.

I resigned on May 20th. At joining, I was told verbally that the notice period is 1 month, and my offer letter doesn't mention any notice period. Now, the employer insists on a 3-month notice period and says I won't be paid during this period.

Additionally, I requested pay slips around 4 months ago but haven't received any.

My concerns:

• Can the employer enforce a 3-month notice period when none was specified in writing?
• Is it legal to withhold salary during the notice period?
• What can I do about not receiving pay slips?

I'm from a financially weak background, and this situation is causing significant stress. Any advice would be appreciated.