Let me say at the start that I am not a security expert.
With that caveat firmly in mind:
How do I view what viruses or spyware that I have removed from my phone by antivirus apps? Is there a way to pull up that they were at one time there?
That would depend on the "antivirus" app providing a log of what it has done. Check its settings.
When I look at my data usage it says a certain amount was used by deleted apps and users. Is there a way to find out what these are and how much data they have used?
If you had a more detailed monitoring app than the system menu then it might be able to tell you (if it was already installed and running, not retrospectively).
Is there a way to view all of the past wifi networks my phone has connected to?
You can certainly view the list of WiFi networks which have been remembered (turn WiFi on and go to Settings > WiFi and you can see them all). If you've deleted a network (told the phone to forget it) then it's gone.
How can I view a list of times my phone has been remote accessed and from where?
Unless you've already installed an app to do it (e.g.
this one) the system itself is not going to keep a log of network connections for long periods (see also answer to general logging question later).
Is there a way someone could make my phone autoconnect to their wifi even if I do not know their password?
Well if they they already had control of your phone via cellular data (but if so, why bother?) or already had some specialised malware installed on your phone (to sniff a specific network, connect to it if found, then delete it from the list of known networks afterwards, so root privileges needed) you could imagine that. But if they have that level of access and control they could surely get the data off via other routes anyway - if your starting assumption is that the phone is completely owned then all bets are off.
Otherwise, is it possible you might have been spoofed by a fake hotspot (if your phone is set to use any public hotspot services)?
How can I find out how and who has hacked my cell phone?
If it's possible at all it will depend on how it was hacked.
How can I pull up an system activity log or list off everything that has occurred on my phone?
If you enable usb debugging and install
ADB (Android Debug Bridge, part of the Android SDK) on your computer you could use the command "adb logcat" to view longs on a computer connected via usb to the phone. But that log only covers a limited period of time, and if you don't know what you are looking for, or the activity didn't create any log messages, it will be difficult to find anything useful.
How would someone have been able to access phone calls made on my phone. I have a call recorder app, but someone was able to get information I said over confidential phone calls.
I'm going to assume that you are asking how they could access your recordings. Other possibilities include (a) they have their own call recording app installed that you don't know about, (b) they tapped it through the phone network instead (unlikely unless "they" are the security services) or (c) they got the information some other way (don't overlook that possibility).
The simplest way would be if they had physical access to the phone.
The simplest way of hacking a phone is to hack your Google account and gain access to the phone through that. So if you have any suspicion that your phone has been hacked you should change your Google password immediately, and also enable two-factor authentication if you haven't already done so.
Alternatively you can infect a phone via a trojan, i.e. the owner installs an app that actually contains malware (perhaps in addition to what it's supposed to include). Unlikely if you stick to the major app stores, very likely if you install from places that offer pirated software for free. This is unlikely for a targeted attack since it relies on the target picking the particular infected app.
Of course the fact that you know that someone has this information should narrow down the possibilities too (assuming you know something about this person).
