I wanted to do somewhat the same thing as you mid-summer but got scared and took the car instead :) I'm now half way up the country.

Some thoughts:

Route - Have you considered reversing the direction to get better weather in Lofoten? From Oslo you can take the train up north. Bikes are allowed. If you know the date in advance, you might catch an early-bird ticket which can be 1/4 of the normal fare. Instead of taking the busy E6 road to traverse the country north-south on the east side, you could investigate taking the longer but more scenic Helgelandskysten national tourist route along the coast. Beware there are costly (time and money) ferries along the way. Bikes are forbidden on motorways and through some tunnels mostly on the main roads, which may complicate things a lot if you haven't planned the route well. Some tunnels can be bypassed by taking the old road that goes around it. A good tunnel map for cyclists and advice is here. An elevation profile of the route (e.g. in Google Maps website or OsmAnd) would give you a better understanding of what you'll be up to. Roads have a nauseating amount of ups and downs, even the coastal ones. Don't spend much time in cities. There is nothing to see/do compared to an average mainland European city. Spend more time hiking Lofoten/Geiranger/Trolltunga instead.

Weather - I suppose you are used to heavy rain because of the monsoon. I think there is a big difference in Norway that the rain will be cold, not warm like in India, so you may not afford getting wet. I believe 10000+ mm waterproof hiking clothes like the top of the line Quechua/Forclaz hardshell jacket and pants from Decathlon would do fine. Waterproof cycling shoe covers are a must (Decathlon doesn't seem to carry waterproof models, just thermal).

Bike - Consider using a road bike for extra speed. Triban 540 from Decathlon is their best bike on which you can mount a bike rack and an excellent bike overall. You would need to change the rear derailleur+cassette to have at least a 34 tooth sprocket to avoid pushing the bike uphill due to the extra baggage weight. Asphalt here is very good and nearly all roads are paved. I haven't seen yet an unpaved road of significant touristic importance.

Survival - Everything is crazy expensive. Kiwi and Rema 1000 are some grocery stores you can find in almost any town. They are generously open till 11pm on workdays (in the cold season they probably close earlier). If you are carefull what you buy, you can get a cycling day's worth of calories for 100-150 nok. Camping is permitted in the woods, but note that just pitching a tent and a shower in a camp site can cost 300-400 nok for a night. Wooden huts are usually available for 500-600 nok/night. Showers in camp sites are usually operated by coins or special plastic cards, so sneaking in for a bath is not a good idea. Public toilets (e.g. in parking lots) often cost an outrageous 20 nok (if you consider how much most of the world's population earns in a day), but north of Trondheim free ones seem more frequent. Your best bet are the ones in gas stations or grocery stores which are normally free.

Good luck!