Time for Friday Prayer
The time of Friday prayer begins at shar‘ī noon, and according to caution it should not be delayed more than about an hour or two after the beginnings — according to common view — of shar‘ī noon.
 
Friday Prayer by a Traveling Follower
Friday prayer said by a traveling follower is valid and discharges his obligation of performing the noon prayer.

To Say another Prayer behind the Imam of Friday Prayer
It is problematic to perform a prayer other than the Friday prayer behind the imam who is performing the Friday prayer. 

To Reach the Last Rak‘ah of the Friday Prayer
If a person joins the imam during the rukū‘ of the last rak‘ah of the Friday prayer, his prayer is valid and sufficient.