A sublease is the renting of property by a tenant to a third party for a portion of the tenant's existing lease contract. Even if a tenant subleases a property, the original tenant is still liable for the obligations stated in the lease agreement, such as the payment of rent each month. Sub leasing with the consent of the Landlord is legal in India. If the agreement allows the tenant to sublease it, the tenant can sub lease portion of property to third party. When a tenant whose name is on the lease rents a room, a portion of the property, or all of the property to another, it is referred to as subleasing (or subletting). The subtenant must pay rent and comply with the lease terms, but the principal tenant remains ultimately responsible for the lease.

There are formats for sub lease agreement deed hence you cannot make the sub-lease in the manner what you described in the query posted here. 

Obtain written permission from landlord 

enter into registered sub lease agreement 

No its illegal. he can evict you from the premises on this act of yours.

if the lease agreement does not disallow sub-leasing then you can do it because lease agreement is lock-in. 

but if it is rental agreement then the landlord will evict you by ending rental agreement by notice period. You need approval in that case.

It can not be done by writing at back of original rental agreement. 

Unless there is written consent from landlord  to tenant to sublet, tenant cannot sublet the premises under Section 7 of Tamil Nadu Regulation of Rights and Responsibilities of Landlords and Tenants Act, 2017. There is to be positive permission from landlord. Absence of restriction will not help you.  Once tenant sublets landlord  acquires right to seek eviction of tenant. He can file a complaint with Rent Controller which  is Deputy Collector of the District.

- As per law, if a tenant sublets the tenanted premises, and move elsewhere, then they will lose their tenancy right.

- Hence, even the said agreement with landlord having no clause of sub-leasing , then also you need a written consent from him , otherwise the landlord can evict you from the tenanted premises. 

- However, if you got permission from the landlord , then you have to enter into a sub-lease agreement with the said two tenants , and your mentioned way is not valid. 

Your action is unlawful and may attract financial consequences. 

1. No, it is not enough.

2. You shall have to make two separate agreements with your sub-lessees mentioning all the terms and conditions of the said sub-lease.

3. Without registration, neither the lease agreement  nor the sub-lease agreement is valid in the yes of law.   

No, it will not legally serve the purpose. A proper sublease agreement has to be drafted by a competent lawyer and executed between you and the tenants separately, complying with the latest tenancy act enacted in Tamil Nadu. Depending on the lease tenure it has to be registered if required.

Are you really the tenant? Or the landlord itself?

The writing will  be valid if its signed and endorsed by both the parties 

Dear Sir, 

1. You will first need written consent from your landlord that you can sub-lease. If you do not have the same, it can lead to eviction. 

2. You can Sublease it with a sublease agreement with specific details regarding the place, period, rent, expiration date, etc. and you need to inform the same to your landlord within one month. 

• For further assistance, please book a consultation with me.

Execute a fresh agreement with the sub-lessees.