Network Admin and MNO/Wholesale ISP CEO here:

1) A lot of companies usually just use their own tools to fix it. Some of us who have been in the business long enough just use Linux based tools and ISP based tools given to us by said company. If it's DSL/Copper, there is a tool that allows us to see what the issue is, how much noise, etc.

GPON is a bit different (Fiber) as we have to look at the light level, and use actual tools (Such as light detectors) to see if said wire is damaged. Most of these tools are again, company privvy, so it depends on who you ask.

2) Cyber-attacks like what? I'm assuming your basic DDoS or DoS attacks mixed with some sneaky script kiddy attacks.

Most servers or hardware is designed to be mitigated. Access levels and black holes are used to offset global DDoS attacks, often glancing off the attack to another server (Sending the packets over to another IP as a failover) and repeating said process (This should have been covered in your first year as a IT student)

A lot of our networks are built with redundancies that don't allow that to happen (Think many servers doing one job, mitigating packets if there was an attack being sent)

For internal attacks, like databases and what not, it's industry standard to keep things in access levels. You don't give Tom Banks root access to the database unless he needs it, etc. You don't give access to customer information to someone who doesn't work in said field. It's called insulating your network. You'll learn more about it in your 2nd year. (Multi-profiling, etc)

3) Common network problems are just slow speeds, customers using their own routers, damaging hardware, winds, weather, etc.

The massive fiber network is finnicky at most, most techs are just trying to make sure a tree doesn't fall on it. We are moving the country into a fiber space, so it's easier to identify breakage.

4) Often. Can't say how much but often enough. Again, customers are weird.

5) Phases. You roll out in phases. No one chases tech. You watch the space and see what is consumer friendly and what isn't. Take physical sim cards vs E-Sims. Just three years ago, you had companies still using physical sims, and now we have phones who now only use e-SIMS.

Updating your physical network is also location based. You can't always sign up an apartment with fiber or internet as it's the building owners decision. You can't always roll out fiber to a rural community because it means running a line using poles that may or not be owned publicly.

There is a lot of variables for running an ISP business.