Just use a pen in the reset at the back. Make sure you've got the sticker on the bottom and pull out card to re connect assuming you've changed the default settings
As well as doing speed test and a streaming test on a laptop as suggested you could also setup a BQM to see what your connection looks like over 24 hours If you need to post it back here make sure to exclude your IP address
I'm on 200 and across the house there are games, netflix, amazon, now tv and YouTube etc on multiple devices with no buffering (mostly wired unless via phone or tablet)