1. Why is it better to change strings individually ...

1. The guitar's neck is normally held against the tension of the 6 strings. If you take them all off together, the neck will bend because of the truss rod (a metal rod found within the neck). This bent is not problematic, but in order to prevent these bents, you replace a string at a time, thus keeping the neck close to its normal stage

2. Boss tuners are great for realtime (u plug them in your effects chain and can use them during a show). You have also cheaper korg tuners which are great. It really doesnt matter what guitar you are tuning.

3. Depends on your budget. If it's tight, get a mexican or squire mimcs. The wood of the telecaster makes its unique sound, and if u only need to jam, you dont need the best pickups. A friend of mine bought such for 100$ and he performs with it!. The top edge can get to more than 5000$ !!

There are many decent tuners on the market today. My only suggestions to you when out to purchase one for yourself are the following;

1. Decide if you want it in your effects loop or not.

2. Make sure that it is a chromatic tuner no matter what brand you buy. I say this because they have superior frequency acuracy and they work well for setting your intonation as well as your base note frequency. All to often I hear guitars that sound awesome from open to fretted between 5th and 7th frets and then its like you took a tire iron to your axe to play anything above the tenth fret. Proper intonation is critical in the overall sound of any player at any skill level.

Jer...

Strings break one at a time.  If you get a flat, do you replace all 4 tires?  It is common sense to replace only what is damaged.  If it was recommended to replace strings all at once, guitar strings would be sold in six packs, not as individuals.  Strings that get the most use will wear out much more quickly.

guitar strings are sold in packs of six. the reason they are sold individually is so that you can get whatever guage you want for each string. If you only change your strings as they break, then they'll sound like shit and will be almost solid black.

if you have short fingers, go with a guitar that's a short scale, such as a mustang or jaguar, or a gibson.

There's not one certain tuner that's the best. They all do pretty much the same thing, just some do it better. A good one is the Fender PT-100. You can't go wrong with a good, but inexpensive, pedal tuner.