Networking issue in Kali

[Cai-Birdy]

I am really really brand new in Linux. I recently set up a lab for pen testing, but stuck by a few networking issues. Host window10, guest Kali linux, eth0 and eth1(both are in same subnet, also same as host-only adapter ), use both host-only and bridged modes. there are several questions for help:

1. firstly I enabled host-only network mode in virtualbox for Kali. By using eth0, I can ping host-only adapter on host successfully, but cannot ping host ethernet adapter. I think that is how host-only mode works. then I  enabled Bridged mode, I thought there should be a new ethernet interface showing up on host, however, it didn't(until now only two interfaces on adapter settings, one is host ethernet interface, the other is host-only) . my question is whether it is normal... 

2. continued the above scenario...I assumed that is normal...then in bridge mode of virtualbox setting, I selected host ethernet adapter name from dropdown list as the one for bridge. Also configure eth0, eht1, host-only adapter and host ethernet adapter into the same subnet. When I bring eth1 down and bring eth0 up, from host terminal, I cannot ping ip for eth0, but from Kali terminal I can ping host machine and 8.8.8.8, cannot ping host-only adapter, cannot open up google.com in browser(it really confused me...); if I bring eth0 down and bring eth1 down, can only ping host-only adapter. so it appears that eth0 only works for Bridge and eth1 only works for host-only, is that right ?

3. I noticed some posts mentioning that there should be a bridged connection between host-only adapter and one local area connection(also an adapter, in my scenario, host ethernet adapter is supposed to take this role), but I don't think it is true. can you guys advise ?

4, sorry, my question or description of the question are a little mess...words in bold are questions. before entering the real pen testing, I already got so much confusion, thanks a loooooot !