The minimum resolution required for offset printing should be 300 dpi on a single sheet exactly matching used size.
Printing guide
Not all high-resolution photos on the Internet can be used due to license restrictions. First, it should be checked if photo is licensed.
Most probably, an image you have viewed in a website and liked its quality will not be printed well. The suitability of an image for printing is determined by many criteria (size to be used, its original size, format, etc.).
Thin papers and papers of medium thickness i.e. 115 g, 135 g or 170 g, glossy or matt coated paper can be used for standard single leaf flyers such as A4, A5, A6, and 10x21.
115 g, 135 g or a maximum of 170 g glossy or matt coated paper can be used for single-fold A3, single fold A4 and double-fold A4 brochures. Lower weights will seem very weak. If thickness is increased, tear may occur at folding lines due to thickness.
The most important criterion in determining paper weight to be used for a catalogue is how many pages you would need in it. Regarding inner pages of wire-stitched catalogues up to 64 pages, a minimum of 115 g or a maximum of 170 g glossy or matt coated paper can be used.
Lamination can technically be applied on all coated papers on all weights, but in the case of thinner papers than 170 g/m² coated paper, it is not preferred since creasing, folding, stitching etc. after application of lamination cannot be made properly.
Lamination allows printed products to be protected against water, light, tearing and other external factors. Therefore, it is preferred for long-term used items such as books or notebook covers and menus. Matt and glossy types are available.
No, it is not the same. Actually, the colors you see on your screen and the colors you see on another computer screen may not be the same too. Therefore, the colors seen on screen are not a 100% accurate reference point for printing.
If your printer's output quality is sufficiently good, then yes. However, if you have the misconception that the document you are editing to finalize on your computer is suitable for offset printing, then you are mistaken.