Ad supported free version is at https://play.google.com/store/apps/details?id=com.srapps.autoanswerandlimitcalltimelite
Works well with android 5.0 lollipop version also.
Features:
1.Auto answer all calls
2.Auto answer contacts
3.Can set delay to autoanswer
4.speaker on/off mode when auto answered
5.limit call time i.e automatically hang call after specific time
6.option to limit call time for incoming calls or outgoing calls
7.Include/Exclude numbers to auto answer
8.App protected with default password 12345 (can be changed any time)
More info:
1.Please enter number in any settings,as it will display in incoming or outgoing call screen. usually with country code as prefix(Ex:+91 in case of India)