Div2D

// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
// #pragma comment(linker,"/stack:200000000")
#include <bits/stdc++.h>
using namespace std;

#define DEBUG
#ifndef DEBUG
    #define endl "\n"
#endif

#define PI 2*acos(0.0)
#define INFLL 1e18
#define CLEAR(x,val) memset(x,val,sizeof(x))
#define print(x) cout << x << endl, exit(0)
#define watch(x) cerr << #x << " -> " << x << endl
// #define int long long

typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;

const int INF = 1000000000;
const int MOD = 1000000007; //998244353

const int dx[]= {1,0,-1,0,1,-1,1,-1};
const int dy[]= {0,1,0,-1,1,1,-1,-1};

void show(const vector<int> &vec) {
    cout << vec.size() << endl;
    for(int val : vec)
        cout << val << " "; cout << endl;
}

signed main()
{
    //freopen("","r",stdin);
    //freopen("","w",stdout);
    cin.tie(0), cout.tie(0);
    ios::sync_with_stdio(0);
    int q;
    cin >> q;
    while(q--) {
        int n;
        cin >> n;
        int a = 0, b = 0, c = 0, d = 0;
        vector<string> v(n);
        map<string,bool> mp;
        for(int i = 0; i < n; i++) {
            cin >> v[i];
            mp[v[i]] = true;
            if(v[i][0] == '0' && v[i].back() == '0')
                ++a;
            if(v[i][0] == '0' && v[i].back() == '1')
                ++b;
            if(v[i][0] == '1' && v[i].back() == '0')
                ++c;
            if(v[i][0] == '1' && v[i].back() == '1')
                ++d;
        }
        if(b == 0 && c == 0) {
            if(!(a && d))
                cout << 0 << endl;
            else
                cout << -1 << endl;
        }
        else {
            vector<int> res;
            if(b > c) {
                for(int i = 0; i < n && abs(b-c)>1; i++) {
                    if(v[i][0] == '0' && v[i].back() == '1') {
                        string str = v[i];
                        reverse(str.begin(), str.end());
                        if(!mp[str]) {
                            res.push_back(i+1);
                            --b, ++c;
                        }
                    }
                }
            } else {
                for(int i = 0; i < n && abs(c-b)>1; i++) {
                    if(v[i][0] == '1' && v[i].back() == '0') {
                        string str = v[i];
                        reverse(str.begin(), str.end());
                        if(!mp[str]) {
                            res.push_back(i+1);
                            --c, ++b;
                        }
                    }
                }
            }
            if(abs(b-c) > 1)
                cout << "-1" << endl;
            else
                show(res);
        }
    }
    return 0;
}