Readonly Grid, Delete functionality

go through this  - delete from data store entity here you can find two ways   
you can use a process model - > on saveinto parameter of "DELETE" button you can start a process and pass parameter(selected rows to be deleted) 
or you can use direct expression in interface also

A solution could be to have the selectable rows populate an list with the row identifier. Then use that list as the input for a multinode instance in a process model to delete the desired rows based on the IDs

There are 2 ways of doing it and you can decide based on your requirement. 

1. Store all the selected row's identifiers in a variable and then use a!deleteRecords directly from the interface in a dynamicLink's saveInto. 
2. Store all the selected row's identifiers in a variable and then start a process on dynamicLink's saveInto in which you call the same smart service.

Now if you want to generate the memory footprint and so some more operations in addition to deleting the data, you can use the second option or else first option should be fine. 

This is not exactly what you are expecting. But this implementation can give you some idea for your usecase implementation.

I am trying with the option-1, but I did not find a!deleteRecords.

I am using version 21.4, I am not sure a!deleteRecords is available after 21.4 version.

you can use a!deleteFromDataStoreEntity 

a!deleteRecords() function was introduced in 22.3 version. In your case, you can use  a!deleteFromDataStoreEntity() function.