Hello and welcome to the forum, thank you for the introduction
There is plenty here to absorb as you progress with your scope but you will find as your knowledge and confidence increases, it will reveal the limitations of your scope
I must be in bad luck. My 4425A has a bad 4th channel, the D.
Probably cold solder joint somewhere.
Press hard and keep pressing on the BNC+ connector and only then the signal and the auto-recognition BNC+ works , Bad QC on this one.
I am discussing with AESWave* ( *where I bought it from ) on how I can swap for a new one fast.
Dang, I am 20+ hours and 1/2 a globe away by flight from AESWave.
At the least the first 2 days I was enjoying 4425A's channel A and B and its better resolution and memory over the 2205A and more importantly the floating ground 4425A has. Awesome device, I love it.