The recommended pressure to inflate a tyre to is usually embossed on the tyre's sidewall, often as minimum and maximum figures rather than an exact target. There are a number of factors to consider when deciding how hard your tyres need to be fixed.
Any single-speed or standard derailer chain can be connected with a chain tool. Narrow 9, 10 or '11 speed' chains have plates that are too thin to make this a reliable process and connect with special links that are supplied with them. Some chains – for example Shimano - have to be broken and reconnected with a special pin. Others with a trick link that can be dismantled by hand.
wheel spokes go into a hole in the hub flange and held there by a head. Spokes usually have a 90 degree bend at the head-end but some hubs are designed for straight spokes. If you are replacing a spoke it needs to match the others in shape and length.