Fahrradwesten

Yes they do! You, your ride mates and your bike will keep cleaner on filthy rides if you fit mudguards. The extent to which they work depends on your bike and the type of mudguards fitted. Fitting full mudguards and mudflaps gives the best coverage, if your road bike will fit them. Even short mudguards on MTB's can do a decent job of reducing the amount of mud and gloop spraying up.

Bike riding in winter is more comfortable if you can keep drier. Mudguards can help you stay drier and avoid getting covered in spray from the roads and trails.

Lights are important in darker winter months, both so that other road users can see you, and so that you can see the road / trail ahead, when riding in unlit terrain. Also, riding in daylight with daytime riding lights in winter months makes riders more visable, particularly on gloomy days.

During winter, your bike attracts more filth and dirt than in summer months. Minimise winter's impact on your bike through keeping your bike clean and lubricated.

Possibly, to some extent, but you will likely be restricted in movement and not feel quite as toasty as wearing clothing designed for winter cycling, utilising winter specific wamer fabrics. Bike riding is very uncomfortable in cold weather with unprotected extremities; hands, toes and the head, really need to be kept warm on cold winter rides..

Yes, pretty much, although this depends on where you live. Spring and autumn share some similarities in that the weather can be very changeable with a wide range of weather possibilities - keeping comfotable can be trickier than in summer or winter.

A cool summer / mesh base layer can help insulate your body from the heat of summer. Although it may seem counterintuitive to add an extra layer, they do help keep you cooler. A summer base layer can also absorb sweat and keep you feeling fresher for longer.