Landlord Tenant

My landlord is an old man who rented his property to me for some extra source of income. I study in Texas Tech University and am active member of a local band. Every evening we have jam sessions at my place. My landlord has a problem with my friends entering the rental premises. Last night when I reached home with friends for the jam session, I saw that the door locks to my room were changed. The locks were changed so that I could not enter the premises. Is it lawful for the landlord to change the door lock without providing the tenant new keys?

I live in Texas, in a two bedroom rented house. While I was in office yesterday, my landlord came to the premises and removed the door knob to all the doors. The doors were working just fine and they needed no repairs. I am not sure if the landlord did this to make me quit the premises or just to annoy me. Under the Texas landlord tenant laws, what action can I take against the landlord?

I am moving to Texas next month. I have found a job in the Dallas. The house that I have finalized is close to my office but the rent seems to be high. Once I take possession of the rental premises, can I rent one of the rooms to another tenant without taking the consent of the landlord?

I live on a monthly tenancy basis in Texas. I will be moving in with my boyfriend soon so I need to send a notice to quit to my landlord at the earliest. I pay my rent on a monthly basis. Can I mention the date on which I would like the tenancy to be terminated in the notice to quit?

I shifted to New York two months back. At present, I live alone but my wife along with our three children will be relocating to our rented house this month. My landlord is not allowing my family to move in with me. I had informed the landlord well in advance that my family would move in with me once I find a house. Can a landlord restrict the tenant’s immediate family members from occupying the rental premises?