While eating food among devotees, what is the permission word to ask the elder, when we finish and get up before they complete eating?
Responding per my understanding.
In general, it is preferred that we wait for the elders to complete the meal and get up after they do. It is just good manners and makes the elders feel good.
If parishechana was not done at the beginning then there is no need to wait for others to complete their eating. Good manners aside, you can get up and leave. For example, prasadam that gets be served in a temple like tamarind rice or curd rice etc - each one can eat their portion and leave carefully without spilling or falling on others
If parishechana was done at the beginning and after meals, if one has to leave quickly without waiting for all to complete then, as far as i have noted, there are 2 things to be done. One - we request for permission from the elders, stating something like 'adiyen, kshamikkanum'. Two - the person who has served the meals will come and stand in between you and the other group and you can then get up. The logic being that the person/server works as a screen/wall between you and the other group. So you can leave. This process can be repeated more than once. I have seen this in practice in Tamilnadu. But in general, better to stay put and wait for others. Max it will take another 10-15 minutes. And all of them getting up together after meals gives a good community feeling. Fosters relationships.