Friction gear systems are a lot simpler to adjust, because the movement of the derailer cable can be modulated as you ride, every time you change the gear- they require less cycle maintenance. Modern index shifting systems are a little more complicated because each ‘click’ must release the exact right amount of cable to allow the derailer to move the correct distance to move the chain from one gear to another. Setting up and adjusting a derailer is not difficult and requires only basic tools, but there is a methodical procedure to follow.
2) On my second day, the pannier bag fell off and got lost after I stopped for lunch, which required locking up the bike somewhere, so I took the bag into restaurant and re-attached it using the two velcro straps on the rear rack. I've used many panniers before, thought I did it correctly. But apparently I did not. So I paid $55 (cost) to replace everything in bag and bag. In hindsight, I wished I'd put a bungee around bag straps to really secure it to bike. PROBABLY MY FAULT.
Brakes come in a variety of designs depending on the age and style of your bike. Rim brakes offer more modulation but have less stopping power, so are more suited to riding on the roads. Disc brakes can provide huge amounts of stopping power so are best suited to off road riding, although ‘V’ rim brakes are also well suited to mountain biking. All brakes use a friction system to stop the movement of the wheel, so regular checks of the contact pads should form part of your regular cycle maintenance.