If network sends RRC connection release to UE, UE does service request to connect.
Does it do attach request also in any scenario in LTE?
RRC connection release, releases only RRC connection.
UE still has NAS context (Not detached).
In this case, if UE needs to send anything to network (TAU / UL data / Response to paging, etc), it initiates NAS Service request.
It will not contain NAS attach request.
If RRC conn release just triggered by enb, UE in LTE idle mode, UE context is still kept in MME, when UE does service request no need attach because UE still in 4G.
But if RRC release following core network release trigger, or enb release UE to 3G for MLB, UE context is release in MME also, UE has to attach again.