Unfortunately being Europe the situation changes from country to country. But I will try and keep my answer as general as possible.
I most places wild camping is not allowed. Main exceptions are Scotland and Nordic countries and some other places where its illegal but widely tolerated.
I Alpine and other mountainous areas (except in UK) there is a widespread ...
Its nearly just the half of what you would have expected to see.
Honestly I had head-scratched many details for European Long Distance Trails. But I realized that they are so long that even if I plan to complete one of them in sections, it would take multiple years considering my current economic state :-)
By the time I realized that,I already had some data ...
This is an extremely long trail. Very good walkers are able to do 30-50 km (depending on weather and terrain) each day for a very long time. But for seasoned (though physically very fit) walker a realistic estimate is on avg. 25 km/day. So for 7000 km you would need 280 days.
According to the article on outdoorseiten.de the trail part in Romania is not done ...
A general answer to a general question
Long distance through hiking is a fairly well developed activity in terms of common best practices. I would suggest picking up a book on more popular through trails (The Appalachian Trail or Pacific Crest trail in the U.S.) that has many handy suggestions. Take from it what you will based on the terrain you will cover.
There are two conflicting accounts of the route of the E1 through Børgefjell.
After coming back from Børgefjell, I believe that the route through Børgefjell is probably the toughest part of the E1, and a good candidate for the toughest part of any European long-distance hiking route. Within Børgefjell, there are no markers, few trails, few bridges, and ...
I hike in that very area some years ago. We would typically get water from the refuges.
Le refuge de la Balme
Le refuge de la croix du Bonhomme
Le refuge des Mottets
Il refugio Elisabetta
You'll find clean water there, and they are not that far apart (about half a day between each, I'd say).
The rest of the time, if you don't have enough ...
Probably your best solution is to take a small camping stove and boil water you get from a creek. The huts are basically doing the same when they sell you tea water.
In my experience, most bivoucs require you to bring your own stove anyways, so this method hardly adds any weight (maybe some extra gas). It is way cheaper than buying a water filter and it does ...
A through-hike of the E4 would be a major undertaking, at over 10,000k / 6,500 miles. Unless you're a very powerful walker it's going to take you at least 2 years. A section hike would take many years more.
It's difficult to see how you could realistically undertake this without significant funding. The path passes through many areas where wild camping ...
In germany, putting up a tent for the night is OK in many places (except e.g. natural reserves) with permission of the land owner/leaseholder.
The procedure then is to ask locally whether they have a meadow/field/wood where you can camp for the night and LNT when you see someone
at a farm
at the sports ground (they may even have showers)
at the church