Genie and an External Hard Drive

I’ve read posts here on this topic, but we’re quite dated, so here goes. 

I have a Genie DVR in the main TV room and an older HR54 HD DVR in the bedroom. My wife uses the Genie and records shows and old movies she enjoys, and the drive is usually 90% + used I use the HR54 to record sports events and analysis shows. My problem is that the HR54 sporadically looses satellite signal so when I go to watch something I recorded the program shows on the list but there is nothing there. I’ve found that resetting the receiver rectifies the signal issue. 

If I call DirecTv, they will replace the receiver with a Genie client (I have the service plan). I considered buying a used HR 54 but not sure they would activate for me due to the service plan. So my thought is to get a large capacity external HD to plug in. 

1. what is the largest capacity HD DirecTv supports with the Genie?

2. Must the external drive be eSATA or can it be USB?

3. I’ve read that the Genie Ver. 3 does not support external hard drive.  How can I tell if my Genie DVR is Ver. 3.