Early termination of a long-term commercial lease agreement

In case of a long-term lease with a commercial tenant for eg 5 years and the tenant wants to break the contract say after 3 years.

The termination clause in the agreement states that the tenant has to pay a minimum rent for 3 years + termination penalty equal to 6 months + 3 months notice period.

The query is, at the time of termination, lease agreement ceases and the tenant is liable to pay the termination penalty + notice period immediately or as per the terms of the lease agreement?

Assume the tenant wants a payment plan, can he lock up the premise and not hand over the keys till the minimum rent period (i.e 3 years) and whether late payment fees is applicable? (assume the lease agreement states late payment fees for non-payment), if applicable whether the calculation should be from termination date or the lease due dates?

I believe the late payment fees should be from the termination date and not on lease due dates since the lease agreement is terminated by way of the notice.