What is the difference between "since " and " for the past of" ?

For can be used all tense but since can be used only in perfect tense.

For is used to talk about a period of time: three hours, four hours, twelve months etc. . She has been waiting for four hours. . Since is used to talk about a point in the past time: sunday, 6th January, morning, 1971 etc. . It has been raining since morning.

"Since" is use to express perfect time and "for" is use to express imperfect time. For example, we are living here for many years. we are living here since 2015. here in 1st sentence we cant get the exact time but in 2nd sentence we can understand the exact time. that means if u don't have perfect time to mention, use "for" and for perfect time use "since". I hope this information will be helpful to you..

"since " unlimited domain . we can't get the exact "for" denotes afield. exact time