1/2 in. 0.700 OD Compression Elbow

Yes, the fitting can be reused.

The compression fittings with black color inserts are designed for a drip tubing with outside diameter of .700 OD. They also can be used to connect to a drip tubing with outside diameter of .710 OD, but will not hold under high pressure and heat. The compression fittings with blue inserts are designed for a drip tubing with outside diameter of .710 OD. They can also be used to connect to the smaller size, .700 OD drip tubing, but they will be harder to connect, however, they will hold better under very high pressure in any type of weather. David

It is important to know the size of drip tubing used in your installation, in general, the compression fittings used with the correct size drip tubing will provide over time the best connection for a leak free drip irrigation system. Size of drip tubing on the market and manufacturers: Drip tubing with .630 OD (16 mm) available from Rain Drip and Rain Bird: use compression fittings with green insert for the .630 OD or 16 mm barb fittings. Drip tubing with .700 OD (17.8 mm) available from DIG, Rain Drip and Rain Bird: use compression fittings with black insert for the .700 OD. You can use the 17 mm barb fittings with low pressure. Drip tubing with .710 OD (18 mm) available from Toro and DIG: use compression fittings with blue insert for the .710 OD. Do not use barb fittings on this size. The .710 drip tubing will have the highest flow rate rating with lower head loss. David

Yes, this should fit DIG drip line

I do not believe a 3/4" drip line exist. There are other hose (e.g. PEX) with an appropriate compression elbow (SharkBite) that can be used for an outdoor use direct bury application